1. Field of the Invention
This invention relates to a draw bar for a towing tractor employed in a towing operation for an aircraft or a trailer.
2. Prior Art
An example of a conventional draw bar for a towing tractor is shown in FIG. 1. This draw bar is constituted by a draw bar bracket 7 mounted on a weight 2 at the rear of the towing tractor, a draw bar pin is provided for vertical movement in an insertion opening 10 of the draw bar bracket 7, an actuating lever 21 provided near a driver's seat 5 of the towing tractor, and a link unit 25 linking the actuating lever 21 to the draw bar pin 15 and adapted for raising or lowering the draw bar pin 15 on actuation of the lever 21.
The actuating lever 21 is pivotally mounted on a lever bracket 27 on the weight 2 by the interposition of a lever shaft 23. The link unit 25 is constituted by a link 28 secured to the proximal end of the actuating lever 21 and a link 34 having its one end provided with a connecting pin 35 engaging in an elongated aperture 33 at the end of the link 28 and having its other end rotatably mounted on a head 15a of the draw bar pin 15 by the interposition of a pin 36.
When the actuating lever 21 is rotated from the solid line position to the double dotted chain line position, with the link 28 being rotated in the same direction as the actuating lever 21, the draw bar pin 15 is raised to a receded or out-of the-way position by means of the link plate 34. For towing a trailer, for example when the actuating lever 21 is rotated to its original position, with a connecting opening 13 in a tow bar 12 of the trailer being aligned with the insertion opening 10 of the draw bar bracket 7, the draw bar pin 15 is lowered by its own gravity to the towing position to inter-connect the tow bar 12 to the draw bar bracket 7.
With the above described conventional draw bar, the link unit is arranged in the exposed state on the outside of the weight.
Therefore, during rearward movement of the towing tractor, it frequently occurs that the link unit impinges on some impediment or member to be thereby damaged. Also the link unit exposed on the outside of the weight detracts from the appearance of the towing tractor to impair neatness in design.
A protective cover for the link unit may be annexed to the weight to prevent the above mentioned damage to the weight. However, this again is not a desirable measure since the protective cover similarly detracts from the appearance of the towing tractor.